It appears to be a Venetian chevron but very hard to tell if it is a 6 or 7 layer from your picture. The 7-L's date from the late 15th century and were made in these tiny sizes. It seems that the tiny ones were popular in the South American trade so many are found there in antique bead strands, up to the present times. The 6-L's date from sometime in the 19th century, and they also can be found in very small versions.

The innermost layer on a 7-L is typically a translucent greenish color (but other colors are seen too) and can be quite hard to distinguish especially if the bead has degraded. The 7-L's were also hand-faceted. The 6-L's would typically be ground smoothly at the ends rather than showing discrete flat facets.

Can you please show a photo of the bead from the side?

You can see more information on Venetian chevrons on the www.picardbeads.com web site, exhibits #9 & 10.

I agree with Rosanna: can you, please, send an another pic? because I saw so much fake chevrons which are an elaborate imitation bead with some salt, sand or acid .... to persuade that she is old and it's difficult, sometimes, to see what it's fake or true. We can't see exactly the whole bead and it's a little vague: it's would be better with the whole bead not so near and the from the side. Is it possible?